Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek <NA> none
[10] none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "daily" "oncePerWeek" "severalPerWeek"
sample( lvs, 3 )
[1] "oncePerWeek" "daily" "severalPerWeek"
sample( lvs, 3 )
[1] "none" "severalPerWeek" "oncePerWeek"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] none none daily none severalPerWeek oncePerWeek oncePerWeek none daily
[10] daily oncePerWeek none daily none oncePerWeek severalPerWeek oncePerWeek daily
[19] none daily daily oncePerWeek oncePerWeek daily none severalPerWeek daily
[28] daily daily oncePerWeek severalPerWeek oncePerWeek severalPerWeek daily none daily
[37] severalPerWeek none daily none oncePerWeek none oncePerWeek daily none
[46] daily none severalPerWeek oncePerWeek none oncePerWeek daily none severalPerWeek
[55] oncePerWeek none daily severalPerWeek severalPerWeek daily daily daily daily
[64] oncePerWeek severalPerWeek none oncePerWeek daily daily none oncePerWeek severalPerWeek
[73] oncePerWeek none none daily severalPerWeek severalPerWeek daily daily daily
[82] none severalPerWeek none daily none none oncePerWeek daily oncePerWeek
[91] none severalPerWeek severalPerWeek severalPerWeek daily daily severalPerWeek daily severalPerWeek
[100] severalPerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 26
2 oncePerWeek 20
3 severalPerWeek 21
4 daily 33
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 33
2 severalPerWeek 21
3 oncePerWeek 20
4 none 26